The two are creating "Concert," which will combine premium digital inventory and audiences from both companies' digital assets. The effort will concentrate on display ad inventory to start, but may include digital video moving forward.

The idea is to give advertisers greater reach among particular audiences than either company could provide alone. A marketer trying to reach foodies, for example, could use the program to buy ad space across NBCU content related to Bravo's "Top Chef" and Vox's Eater.com.

Linda Yaccarino, chairman-advertising sales and client partnerships at NBC Universal, said the deal provided a destination for marketers making a "flight to quality" online. Concert will help Vox and NBC Universal continue to offer clients "the best content in a completely safe, premium environment for their creative," she said in an email provided by a spokeswoman.

Vox Media typically reaches an affluent 25-to-34-year-old audience, according to Jim Bankoff, chairman and CEO of Vox Media. "When you pair that up with the NBC audiences, I really think you can hit pretty much any adult demo that you're looking to hit," he said.

"Concert" could expand to include inventory from other publishers that are not NBCU or Vox, according to the companies.

The inventory will be accessible through Vox's ad platform, which it says allows marketers to optimize their creative as campaigns run.

Jeanine Poggi covers the TV industry and how broadcast and cable networks and distributors are adopting to the changes in the world of TV advertising. She joined Ad Age in 2012, following six years covering the retail and media industries and other financial sectors for Women's Wear Daily, Forbes and TheStreet.

Jeremy Barr covers the business of media, with a particular focus on how newspaper, magazine, and digital-native publishers are making money from advertising and other lines of business. He joined Ad Age in November 2015, after serving as an associate editor for Politico Media for over a year and a half. A graduate of Emory University and the University of Maryland's journalism school, he got his start on the media beat as a contributor to Poynter.org.